This invention relates to an ultrafine tube and a method for its production and, more particularly, it relates to a method for producing ultrafine tubes for use as cooling channels in semiconducting integrated circuit elements, columns in microsized analyzer, light-piping channels in photo circuit elements and the like.
Recently, there has been proposed a method for producing ultrafine tubes in Japanese patent laid-open No. 59-56729, which includes the steps diagrammed in FIG. 6. In this method, a substrate (1) is firstly coated with a photosensitive emulsion to form a first positive resist layer (8) which is then coated with a lower photosensitive emulsion to form a second positive resist layer (9) with a photosensitivity lower than that of the first resist layer (8), as shown in FIG. 6a. The first and second resist layers (8) (9) are exposed to light everywhere except in the area beneath the two parallel lines, and then developed, so that the unexposed resist layers are rinsed off, leaving the resist layers in the condition shown in part (b) of FIG. 6. Since the high sensitive emulsion (8) is eroded greatly as compared with the low sensitive emulsion (9), each island (3) of the resist layer will have a thin leg portion (4) and head portion (5). During development, the islands becomes soft and easy to deform, the islands bend in the direction so that their head portions (5) come close to one another and the islands (3) are joined together at their head portions to form an ultrafine tube (6).
However, this method involves complicated steps such as exposure and development. In addition, it is difficult with this method to produce ultrafine tubes with a complicated shape.